This invention relates to a hydrostatic transmission wherein a hydraulic pump is connected with a hydraulic motor in a closed loop and the hydraulic motor is driven by the fluid under pressure delivered by the hydraulic pump to drive the vehicle.
If the amount of leakage of the fluid in the hydraulic circuits of the hydrostatic transmission increases so as to reduce the charge pressure exerted in the hydraulic circuits, then serious troubles such as failures of the hydraulic pump and the hydraulic motor may occur. There has been proposed no effective way to solve the problem.